RNA viruses include viruses that cause HIV, the common cold, hepatitis, influenza, polio, mumps, measles, SARS, Ebola, and other diseases. Vaccination against RNA viruses is one way of protecting populations, both human and animal, from these diseases. In particular, vaccinating against influenza A virus is one means of controlling morbidity and mortality resulting from annual influenza epidemics.
Generally speaking, the immune response induced by a live, attenuated vaccine is believed to be superior to that induced by inactivated virus, resulting in increased protection against antigenic-drift variants and other antigenic subtypes. Live attenuated vaccines, however, potentially pose a greater risk to the host than an inactivated virus. In addition, methods used to attenuate the virus may affect the ability of the virus to induce a protective immune response in the host. Consequently, there is a need in the art for safe live attenuated vaccines that induce a protective immune response against an RNA virus in a host.